Glenn D. Swanson

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Ramp work rate tests have been used to estimate aerobic parameters in exercise stress testing. Previous studies have suggested an assumption of a linear dynamic system for O2 uptake kinetics. The implication is that model parameters estimated from ramp tests should be similar to those estimated from other dynamic tests. In nine healthy subjects, we found(More)
Pseudorandom binary sequence (PRBS) exercise tests involve repeated switching between two work rates (WR) according to a computer-generated pattern. This paper presents an approach to analysis of O2 uptake (VO2) in the time domain. First, the autocorrelation function (ACF) of the input WR was recognized to be a triangular-shaped pulse that can be taken to(More)
A dynamic end-tidal forcing technique for producing step changes in end-tidal CO2 with end-tidal O2 held constant independent of the ventilation response or the mixed venous return is introduced for characterizing the human ventilation response to end-tidal CO2 step changes for both normoxic (PAO2 = 125 Torr) and hypoxic (PAO2 = 60 Torr) conditions. The(More)
Traditional approaches to estimating a lactate threshold during a progressive exercise test have utilized visual inspection of the data. We describe a computerized approach which utilizes a log-log transformation to yield two approximately linear segments. Linear regression lines are fit to these segments and the intersection of the two lines yields an(More)
The ventilatory response to changes in alveolar (arterial) CO2 is widely used as an index of respiratory control behavior. Methods for estimating these response slopes should incorporate the possibility that there may be errors in both the independent (partial pressure of CO2) and dependent (ventilation) variables. In a recent paper Daubenspeck and Ogden(More)
Subjects voluntarily hyperventilated for 10 breaths. A dynamic end-tidal forcing technique manipulated inspired gases to hold end-tidal CO2-O2 tensions at normal values during the voluntary ventilation period and the postvoluntary ventilation recovery period when the subjects returned to spontaneous breathing. Six of the seven subjects studied exhibited a(More)
A numerical method for fitting linear compartmental models to data is presented which is similar to the method proposed by Jennrich and Bright (R. I. Jennrich and P. B. Bright, Technometrics 18, 385 (1976] and Feldman (H. A. Feldman. Amer. J. Physiol. 233, R1 (1977] but avoids some of the numerical difficulties. The method is direct and does not use(More)
The shape parameter, A, has been used to assess hypoxic sensitivity (ventilatory response, VE, to lowered alveolar oxygen tension, PAO2) in the model of the form VE = VEO + A/(PAO2 - C) where C is held constant at 32. In this paper we examine the consequence of holding C constant versus estimating both A and C from the data. Using computer-simulated data(More)